Known coupling devices comprise, mostly, a jib or draft bar fixed rigidly to the trailer and whose free end is designed to be hooked to the rear of a towing vehicle.
It is generally very difficult to manoeuver in reverse, a trailer coupled to the towing vehicle by means of the aforesaid device. If the trailer is not initially perfectly aligned with the towing vehicle, as soon as the latter starts to move back, the trailer has a tendency to pivot with respect to the towing vehicle, thereby departing from the path desired by the driver. Through this fact, manoeuvres rearwards can only be carried out for very short distances.